On screen display (OSD) arrangements employed in video processing systems include a switching (or "multiplexing") network for switching between graphic image representative signals and normal video signals so that a graphic image can be displayed on the screen of a picture reproduction device either in place of the image represented by the video signals or together with (inserted in) the image. The graphic image can take the form of alphanumeric symbols or-pictorial graphics, and can be used to indicate status information, such as channel numbers or time, or operating instructions.
In an OSD arrangement for use in an analog video signal processing system, the multiplexing network typically operates to switch in levels corresponding to the desired intensity of respective portions of the graphic image at the time the graphic image portions are to be displayed. In such an arrangement the graphic image representative signals take the form of timing pulses which occur when the graphic image portions are to be displayed and are used to control the multiplexing network. Such an analog OSD arrangement can also be used in a digital video processing system, but requires that the video signals be first converted to analog form. While digital video signal processing systems typically include a digital-to-analog converter section in which the digital video signals are converted to analog form, it may be more cost effective for the OSD arrangement to be incorporated as an integral part of the digital video processing section.